1. Field of the Invention
The present invention relates to an information reproduction head apparatus for reading an information signal recorded on a magnetic medium and an information recording/reproducing system using the information reproduction head and in particular, to an information reproduction head apparatus and an information recording/reproducing system realizing a small-hysteresis R-H loop and including yoke type magnetoresistance effect sensor using a tunneling magnetoresisstivity (TMR).
The present invention also relates to an information reproduction head apparatus for reading an information signal recorded on a magnetic medium, and to an information recording/reproduction system using the information reproduction head and in particular, to eliminate a positional interference between the front yoke portion and the bottom electrode, so as to enable to obtain the dynamic path of the front yoke portion and the electro-conductive characteristic of the bottom electrode.
2. Description of the Related Art
As a conventional technique, a magnetic read converter called magneto-resistance effect (MR) sensor or head has been disclosed. Here, a data is read from a magnetic surface with a high linear density. The MR sensor detects a magnetic signal through a resistance change as a function of a magnetic flux intensity and direction detected by a read element.
This conventional MR sensor operates according to the anisotropic magnetic resistance (AMR) effect in which one resistance component of the read element changes in proportion to cosine of the angle defined by the magnetization direction and the electric current flowing through the element. The AMR effect is detailed in D. A. Thompson et al xe2x80x9cMemory, Storage, and Related Applicationsxe2x80x9d, IEEE Trans. on Mag. MAG-11, p. 1039, (1975).
In the magnetic head using the AMR effect is usually subjected to longitudinal bias so as to suppress the Barkhausen noise. This longitudinal bias is applied using FeMn, NiMn, nickel oxide and other antiferromagnetic material.
Furthermore, recently it is described that the more remarkable resistance change of the layered magnetic sensor is caused by an electron spin dependency between magnetic layers sandwiching a non-magnetic layer and accompanying spin-dependent scattering on the boundary surface. This magneto-resistance effect is called xe2x80x9cgigantic magneto-resistance effectxe2x80x9d, xe2x80x9cspin valve effectxe2x80x9d, or the like. Such magneto-resistance sensor is made from an appropriate material and has a higher sensitivity and greater resistance change than the sensor using the AMR effect.
In this type of MR sensor, a pair of ferromagnetic layers isolated by a non-magnetic layer changes in proportion to the cosine of the magnetic direction angle of the magnetization directions of the two ferromagnetic layers.
On the other hand, Japanese Patent Publication A2-61572 discloses a layered magnetic structure which brings a high MR change caused by the non-parallel arrangement of the magnetization of the magnetic layers. The layered structure may be made from a ferromagnetic transient metal or alloy. Moreover, it is disclosed that one of the at least two ferromagnetic layers isolated from each other by an intermediate layer is fixed by a FeMn.
Furthermore, Japanese Patent Publication (unexamined) A4-358310 discloses an MR sensor having two thin film ferromagnetic layers isolated from each other by a non-magnetic metal thin layer. If a magnetic field applied is 0, the magnetization direction of the two ferromagnetic thin film layers intersect vertically and the resistance of the two non-connected ferromagnetic layers changes in proportion to the cosine of the angle defined by the magnetization direction of the two layers, which is independent of the current flowing in the sensor.
Moreover, Japanese Patent Publication (unexamined) A4-103014 discloses a ferromagnetic tunneling magnetoresistivity of a multi ferromagnetic layers inserted by an intermediate layer, in which at least one of the ferromagnetic layers is subjected to a bias magnetic field from an antiferromagnetic body.
Furthermore, Japan Mag. Society, proceeding, 1996, page 135 describes a tunneling magnetoresistivity constituted by a free magnetic layer made from Co and a fixed magnetic layer made from NiFe.
Moreover, Japanese Patent Publication (unexamined) A10-162327 discloses a tunneling magnetoresistivity (TMR) apparatus and magnetoresistance (MR) read head configuration. The TMR apparatus is applied to a so-called shield type magnetoresistance read head, and no description is given on the yoke type information reproduction head having a TMR element with a longitudinal bias layer under a particular condition.
When producing a yoke-type MR sensor using a ferromagnetic TMR junction element, there is a problem that the loop corresponding to the inversion of the free layer of the R-H loop has a high hysterisis and accordingly, when a magnetic information recorded on a magnetic recording medium is reproduced by the sensor, the reproduction waveform has much Barkhausen noise.
It is therefore an object of the present invention to provide a yoke-type magnetoresistance effect (MR) sensor realizing a small-hysteresis R-H loop and using a tunnel junction element capable of obtaining a preferable reproduction waveform.
Moreover, in a conventional magnetoresistance effect element using a ferromagnetic tunnel junction, among the elements constituting the ferromagnetic tunnel junction, one of the free magnetic layer and the fixed magnetic layer is used an upper electrode and the other is used as a lower electrode.
However, in such an element, the element resistance is affected not only by the tunnel resistance but also electrode resistance of the lower and upper ferromagnetic layers. Accordingly, the resistance change becomes smaller and the current does not flow uniformly in the tunnel junction element.
For this, the free magnetic layer and the fixed magnetic layer cannot be used directly as electrodes but a small-resistance layer should be provided as an upper electrode and a lower electrode.
On the other hand, in the yoke type head, the magnetic flux taken from the medium by the front yoke should be effectively introduced to the free magnetic layer so as to obtain a greater reproduction output.
For this, it is necessary that the yoke end portion and the free magnetic layer end portion be located at close positions. When using a ferromagnetic tunnel junction element constituted by a free magnetic layer, a non-magnetic layer, a fixed magnetic layer, and fixation layer, the yoke should be provided immediately under the free magnetic layer and partially overlain.
However, the lower electrode also should be located under the ferromagnetic tunnel junction element. Thus, even if designed correctly, positional competition brings about a problem of an element production accuracy. The yoke is overlain with the electrode, which causes various problems of electric characteristics, magnetic characteristics, and head production.
Accordingly, another object of the present invention is to provide a yoke type information reproduction apparatus in which there is no interference between the front yoke and the lower electrode so as to obtain simultaneously a magnetic path of the front yoke and an electric path of the lower electrode, and to provide an information recording/reproduction system using the yoke type information reproduction apparatus as a second embodiment of the present invention.
The first embodiment employs various basic techniques to achieve the aforementioned object. That is, the information reproduction head according to the first embodiment of the present invention is a yoke type information reproduction head apparatus including a substrate on which a magnetic sensor block is provided via a non-magnetic insulation layer. The magnetic sensor block is connected to a magnetic pole. The magnetic sensor block includes a ferromagnetic tunnel junction element sandwiched by the upper electrode and the lower electrode. The tunnel junction element is connected a bias layer for magnetic domain control.
The second embodiment, in order to achieve the aforementioned object, employs a technical configuration as follows. A magnetic sensor block is mounted on a substrate via a non-magnetic insulation layer and the magnetic sensor block is a connected to a yoke block, constituting a yoke type information reproduction head apparatus, including a front yoke portion provided in a direction where a medium exists with respect to the tunnel junction element and a rear yoke portion in the opposite direction with respect to the tunnel junction element, wherein at least a part of the front yoke portion and at least a part of the lower magnetic pole are located on different surfaces of the tunnel junction element.